Page 24 - EngineerIT May 2022

ELECTRONICS

Figure 7: Highly integrated, most efficient negative output DC-DC
converter.

are the industry’s smallest and highest efficiency synchronous Figure 9: The MAX17579/MAX17580 in a system using negative
voltage rails.
inverting DC/DC step-down converters. Figure 7 shows their
typical application circuit.
The MAX17577 and MAX17680 have a wide input voltage At 88.5% efficiency, the device dissipates only 292mW while
range. The devices operate from 4.5V to 60V input and can delivering 2.25W power to the load. 292mW means 37% less
deliver up to 300mA output current. With integrated level heat for the system to cool compared to the 460mW of the
shifters, these devices conserve up to 72% of board space by legacy solution shown earlier.
reducing component count by half while using 35% less energy Figure 9 shows an improved version of Figure 2, eliminating
than the closest legacy solution. Figure 8 shows MAX17577 peak the level shifters. The system micro-controller can communicate
efficiency at 88.5%, measured at 16V input and -15V/150mA directly with MAX17579/MAX17580 even though they have
output. This is 5.5% points of higher efficiency compared to the different grounding references.
legacy solution shown in Figure 6. Why is efficiency important? It is also worth noting that with a wide operating voltage
range, these new solutions can withstand and tolerate system
voltage fluctuations such as power surge event, back EMF and
cable voltage ringing, etc. and increase system reliability. In
addition, there are the MAX17577 and MAX17578, which are in
the same family with similar performance, but can deliver up to
1A of output current. These devices are great for powering RF
power amplifiers, GaN FET gate drivers, IGBT gate drivers, etc.

Conclusion
Growing requirements for smaller solution size and lower
heat generation in devices in factory automation, building
automation, and communications systems impose big challenges
for designers looking for negative voltage DC-DC converters,
where most legacy solutions are outdated, inefficient, complex
and bulky. A new breed of highly integrated device with onboard
level shifters, synchronous rectification, wide operating input
voltage, brings to the table the most compact, highly efficient
Figure 8: MAX17579 efficiency at -15V output. and robust negative output DC-DC solutions. n

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